1. Field of the Invention
The present invention relates to a nitride semiconductor device having a structure obtained by forming group III nitride semiconductors on a substrate and a method of manufacturing the same. Group III nitride semiconductors are group III-V semiconductors employing nitrogen as a group V element, and typical examples thereof include aluminum nitride (AlN), gallium nitride (GaN) and indium nitride (InN), which can be generally expressed as AlxInyGa1-x-yN (0≦x≦1, 0≦y≦1 and 0≦x+y≦1).
2. Description of Related Art
A semiconductor light emitting device having a structure obtained by growing a group III nitride semiconductor layer on a GaN substrate is known in general. Typical examples thereof include a blue light emitting diode and a blue semiconductor laser. In addition to such light emitting devices, the group III nitride semiconductor is applied to transistors such as a power transistor and a high electron mobility transistor.
In the case of the light emitting device, the group III nitride semiconductor layer has a multilayer structure obtained by stacking an n-type GaN layer, an active layer (light emitting layer) and a p-type GaN layer from the side of the GaN substrate, for example. According to this structure, electrons and positive holes are recombined in the active layer to emit light.
A group III nitride semiconductor substrate made of GaN or the like is inferior in cleavability as compared with a substrate made of GaAs or the like generally applied to a light emitting diode or a laser diode. If division guide grooves such as scribing lines are formed in a step of dividing the semiconductor substrate into individual chips, dividing positions deviate from the division guide grooves in a subsequent breaking step, and the chip shapes cannot be stabilized.
In order to solve this problem, deep division guide grooves may be formed on a GaN substrate by laser processing (refer to Japanese Unexamined Patent Publication No. 2005-116844). When the grooves are formed on the surface of the substrate, however, the substrate material is heated and scattered around as debris, to adhere to the surface of the substrate and contaminate the same. This debris causes a defective appearance, defective die bonding, defective wire bonding, etc.